The present invention relates to the field of acoustic pods attached to seismic streamers in marine geophysical operations. More particularly, the invention relates to an acoustic pod integrated with the streamer.
Marine seismic streamers are towed behind a seismic vessel in geophysical operations. Acoustic pods and other devices are attached to the streamer exterior to generate signals indicating the streamer section location. Acoustic pods typically include control electronics, waveform generator, and detection circuitry. The acoustic pods sometimes rotate axially around the streamer to maintain the vertical orientation of the acoustic pods as the streamers rotate in the water.
Control signals for controlling the acoustic pod operation are typically transmitted through the streamer exterior surface with electromagnetic devices. However, electric power for conventional acoustic pods is supplied with batteries attached to the acoustic pod exterior of the streamer. The acoustic pods and integrated battery are attached to the streamer exterior as the streamer is deployed from a tow vessel into the water, and are removed from the streamer exterior as the streamer is withdrawn from the water with storage reels.
Conventional acoustic pod deployment is inefficient for several reasons. Batteries are expensive and have a relatively short life of approximately thirty days. To replace depleted or nearly depleted batteries, seismic data collection must cease while the streamer is recovered aboard the seismic vessel or a streamer maintenance vessel locates and replaces the discharged battery. With the increased length and breadth of marine seismic arrays, there is increased demand for acoustic power from the acoustic pods. This increased demand drains the batteries even more rapidly and requires more frequent battery changes.
Conventional acoustic pods are attached to the streamer exterior and generate additional drag in the water. Such drag wastes fuel and generates undesirable "noise" which contaminate the desired seismic signal. Dangling acoustic pods present surface discontinuities which snag other streamers, fishing nets, aqueous vegetation, and otherwise increase streamer damage.
In addition to these limitations, deployment and retrieval of acoustic pods requires significant handling time on the seismic vessel deck. The dangling acoustic pods cannot be stored on the streamer reels, and must be removed when the streamers are stored on board the vessel deck. Such deployment and retrieval requires many personnel hours, delays data gathering operations, and significantly adds to the cost of seismic operations.
Because of these limitations, a need exists for an improved technique for deploying acoustic pods with marine seismic streamers.